微灌管网水力解析及优化设计

随着工业与农业的发展，人口与经济的增长，农业、工业和城市用水将不断增加，水资源危机加剧。我国是一个农业用水大国，发展农业高效节水技术，无疑是缓解水资源矛盾，保障我国经济可持续发展的一项根本性的战略措施。随着农业高效节水技术的发展，微灌这种高效的节水灌溉技术也将得到快速发展和应用，同时全国各地在微灌管网工程建设和运行管理方面的资金投入也将不断增加。通过应用优化设计的理论、方法与工具，寻求使微灌系统灌水质量高、投资少、能耗低的微灌管网系统优化设计方案，可以产生巨大的经济效益。然而，目前对微灌毛管的水力解析与优化设计的研究主要还是基于一些近似假定基础之上；对田间管网的优化研究主要集中在允许压力差的支管及毛管分配比上，没有整体与系统的优化研究；对干管管网优化主要集中在高效算法的研究上；微灌管网优化设计应用上的研究较少，能够在设计中广泛、可靠应用的管网优化计算机设计软件还很少见。针对微灌管网水力解析及优化设计中存在的问题和不足，本文主要进行了以下几个方面的研究。分别提出单向毛管、双向毛管、等量出流毛管的水力解析方法与优化设计模型，给出优化算法的求解方法。适用于变管径、非均匀坡、不等间距灌水器及不同灌水器型号等各种条件下毛管的水力解析与优化设计问题，也可以对设计好的毛管进行水力解析及校核。建立了田间管网水力解析的遗传算法模型和各种已知条件下的田间管网优化设计模型，提出了相应的求解方法。将田间管网作为一个整体进行优化设计，直接以设计灌水均匀度或流量偏差率和灌水器设计流量为设计控制参数，不再采用毛管和支管的等量出流假定，也不需要进行田间管网压力差的分配，计算过程得以简化，可以获得0.05%以上的计算精度。对灌水器工作压力、地形坡度（下坡为负）、流态指数、灌水器间距、堵塞情况、流量偏差率、毛管管径和毛管长度与灌水均匀度的关系进行了分析与研究。研究表明，灌水均匀度对灌水器堵塞百分率的变化最为敏感，对流量偏差率的变化反应较不敏感；随地形坡度的减小，流态指数大的灌水器灌水均匀度随工作压力增加呈递减趋势，流态指数小的灌水器灌水均匀度呈递增趋势；适当增加管径可以提高灌水均匀度，但在下坡条件下，增加管径有时会降低灌水均匀度；保持毛管长度不变，灌水均匀度随灌水器间距的增大而增加；灌水器间距不变，毛管长度增加灌水均匀度降低。对灌水器典型值及其孔口位置进行分析，发现灌水器的典型值与地形坡度和流态指数关系紧密，但其孔口位置只与地面坡度关系密切，与灌水器流态指数无关。 建立了自压和机压树状管网及自压和机压滴灌干管管网优化设计的数学模型，设计了遗传算法求解方法。综合应用了线性规划和非线性规划的优点，假定管网中每一管段最多只能由两种或一种管径的管道组成，模型及算法简单易用，优化变量少，计算精度能够满足微灌管网设计的需要，无需预先确定备选管径组，获得的管径为标准管径，也不需要进行圆整化处理。采用了全局优化搜索算法，可适用于大规模微灌管网的优化设计。首次应用遗传算法进行微灌毛管及田间管网的水力解析和优化设计，建立了新模型，提出了新算法，为微灌毛管及田间管网水力解析和优化设计开辟了一条新思路，提出了解决微灌管网问题的新方法和新途径。应用多重群体遗传算法、模拟退火惩罚技术求解管网优化问题，保持种群的遗传多样性，扩大了搜索范围，增强了搜索作用，保证算法最终稳定收敛到全局最优解。在毛管和田间管网的水力解析与优化设计中，设计了实数编码、算术交叉算子和实数变异算子，提高了计算精度，增加了计算的方便性，保证计算结果在解的可行域内。为每个问题编写了相应的Visual Basic6.0程序，进行了大量模拟计算、实例验证及校核分析，证明所建立的模型与算法计算精度和搜索效率高、可靠性强、收敛性和稳定性好，并且算法程序的运行时间短，具备很好的实用性和通用性。
活动房
With the development of industry and agriculture and increase in population, the water consumption in rural areas and cities will increase constantly, and a severe shortage of water resources will exist in the future. Developing efficient agricultural water-saving techniques will be an essential strategic step to lessen the shortage of water resources and ensure the sustainable economic development of China, a large agricultural country. With the development of efficient agricultural water-saving techniques, the microirrigation technique will be rapidly developed and applied. Meanwhile, the investment in building and running the microirrigation pipe networks will increase in the whole country. Seeking the optimum plan of microirrigation pipe networks with the higher irrigation quality, lower cost of investment and lower consumption of energy can produce great benefits in economy by using the optimal design theory, methods and tools.However, the present study on hydraulic analysis and optimum design for laterals is still based on some approximate presupposition, the optimisation for submain units focuses on the distributive rate of the allowable pressure deviation without systemic and unitary optimisation, the optimisation for main pipe networks focuses on the efficient algorithm, but the applied research on microirrigation pipe networks are insufficient, and the softwares that can be reliably and widely applied to pipe networks optimization are difficult to find. Aimed at the problem and insufficiency of hydraulic analysis and optimum design for microirrigation pipe networks, several problems have been solved in this paper.The hydraulic analysis and optimal design models for single, two and equal outflow laterals are created, and solutions have been put forward. These methods are suited to resolve all kinds of problems with hydraulic analysis and optimal design for laterals, and the existing laterals can be analyzed and checked. The hydraulic analysis and optimal design models under different conditional submain units are created, and the solutions have been put forward. According to these models, the submain units are regarded as a whole and the uniformity or percentage of discharge deviation and designed discharge of irrigator are taken as restraining parameter to optimisation. Meanwhile, the equal outflow presupposition of laterals and submains are no longer adopted, so the computational procedure is simplified and computational accuracy is improved.The between of uniformity and operating pressure of irrigators, gradient, exponent of flow form, spacing between irrigators, clogging conditions, percentage of discharge deviation, lateral diameter and length are analysed and studied. The results indicate that the variation of clogging percentage is the most sensitive factor to uniformity, and the variation of percentage of discharge deviation is hardly sensitive to uniformity; with the gradient decrease, the uniformity of irrigators having the bigger exponent of flow form decreases gradually, but the uniformity of irrigators having the lesser exponent of flow form increases gradually, when the operating pressure of irrigators increases; when the lateral diameter increases, the uniformity improves generally, but sometimes it is likely to reduce under the downgrade condition; when the spacing between irrigator increase and the lateral length does not change, the uniformity will increase; with the lateral length increase, the uniformity decreases. According to the analysis of the eigenvalue and location of irrigator we can reach a conclusion that the eigenvalue has the close correlation with the gradient and exponent of flow form, while the location has only close relation to the gradient, but no relation to the exponent of flow form.The mathematical models of gravity and pumping tree pipe networks and the gravity and pumping pipe network of drip irrigation have been established, and the solution to genetic algorithms has been put forward. Taking the advantage of the linear programming and nonlinear prog